(a) Field of the Invention
The present invention generally relates to a manufacturing method of a solar cell.
(b) Description of the Related Art
A solar battery is a device that converts photonic energy, e.g., solar light energy, into electrical energy using a photoelectric effect.
It is important to produce clean energy, also referred to as next-generation energy that can replace existing fossil fuel energy, that causes a green house effect due to carbon dioxide (CO2) discharge and atomic energy that pollutes the earth's environment, such as via atmospheric pollution by radioactive waste, for example.
A solar cell that uses silicon as a light absorption layer may be classified into a crystalline substrate (e.g., wafer) type solar cell and a thin layer type (e.g., amorphous, polycrystalline) solar cell.
In addition, the various types of solar cells include a compound thin layer solar cell that uses copper indium gallium selenide (CIGS or CuInGaSe2) or cadmium telluride (CdTe), a group III-V solar cell, a dye sensitized solar cell, and an organic solar cell, for example.
A basic structure of a solar cell typically has a conjunction structure of a P-type semiconductor and an N-type semiconductor, such as a diode, and if light is absorbed in the solar cell, electrons having a negative (−) charge and holes having a positive (+) charge caused by the removal of the electrons from atoms are generated by interaction of the light and a material that constitutes a semiconductor of the solar cell, such that a current flows while the electrons and holes move through the solar cell.
This phenomenon is called a photovoltaic effect. In the P-type and N-type semiconductors that constitute the solar cell, the electrons are drawn to the N-type semiconductor and the holes are drawn to the P-type semiconductor such that they move to electrodes that are connected to the N-type semiconductor and the P-type semiconductor, respectively, and if the electrodes are connected to wires, a current flows through the electrodes and the wires, thereby generating electric power.
In a back contact solar cell, which is one of the structures of the solar cell, all of a P-type semiconductor, an N-type semiconductor, and metal grids that are connected thereto are disposed in a rear side of the solar cell where a front side of the solar cell absorbs incident light.
One method of increasing cost competitiveness and efficiency of the back contact solar cell without increasing a number of processing steps required in its manufacture, is by decreasing shunt resistance of the solar cell.